The utilization of automatic door controls and operator mechanisms for regulating the opening and closing movements of doors in commercial buildings, such as supermarkets, banks, department stores and the like, is a familiar part of the American scene. Normally, such automatic door operators are actuated by a mat switch or other suitable control, responsive to the passage of human traffic. Automatic door operators of this type may embody hydraulic, pneumatic or electro-mechanical systems for supplying the necessary door opening and closing forces. In employing electro-mechanical operators, which normally embody a drive-motor and mechanical drive train, it is particularly essential that the drive mechanism be protected against overload forces, such as may occur in the fully open position of an associated door, by reason of heavy wind loads or by the accidental or intentional application of manual forces on the door.
In the past, a variety of hydraulic or pneumatic devices have been used, such as hydraulic dash-pots and check devices, for avoiding impact against a rigid stop in the opening cycle of an associated door; such devices being particularly prevalent in known hydraulic and pneumatic door operators. In still other instances, externally attached hydraulic and rigid or resilient mechanical stops engageably by the door have been employed. However, such prior devices are objectionable not only from an esthetic standpoint, particularly if mounted in non-concealed positions, but for various operating reasons. For example, hydraulic door stops are subject to leakage problems, particularly when light oils or fluids are employed and if heavier fluids, such as grease are used, troublesome blockage of ports and passageways may occur. Further such fluid-operated devices have a relatively long recuperation time as compared to mechanical cushioning devices such as wall or floor mounted compression spring or rubber bumper mechanisms and the like. In addition to the above problems, commercial code requirements demand that inwardly opening doors, operated by automatic control devices, be equipped with a break-away stop feature so that they may be swung outwardly in reverse to their normal opening direction, for emergency exit operation.
Recognizing the foregoing factors, the provision of an effective stop mechanism for use with a motorized door operator of the electro-mechanical class has demonstrated that previously known stop devices, either fluid operated or mechanical, are too large and cumbersome for concealed installations or are otherwise prone to one or more of the aforementioned operational difficulties, thereby rendering them unsuitable for a high-impact resistant, compact stop capable of satisfying the esthetic and operational requirements of a header or under-the-floor installed automatic operator.